The present invention relates generally to a surgical instrument assembly, and more particularly to a method and apparatus for surgically preparing a tibia for implantation of a prosthetic implant component which has an offset stem.
During the lifetime of a patient, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. One such type of joint replacement procedure is a total knee replacement procedure in which a diseased and/or damaged knee joint is replaced with a prosthetic knee joint. A typical total knee replacement procedure utilizes a prosthesis which generally includes a femoral component, a tibial tray, and a tibial bearing insert. The femoral component generally includes a pair of laterally spaced apart condylar portions, the distal surfaces of which bear against a complementary pair of surfaces defined in the tibial bearing insert. The tibial tray typically includes a plate having a stem extending distally therefrom. The stem is implanted in a prepared medullary canal of the patient""s tibia. Once implanted in such a manner, the tibial tray provides a surface on the proximal end of the tibia to which the tibial bearing insert may be affixed.
During performance of such a knee replacement procedure, the surgeon must evaluate the size and condition of the patient""s bones (e.g. the patient""s tibia) in order to determine the proper type and configuration of each of the various types of prosthetic components which are to be implanted. Moreover, the patient""s bones must also be surgically prepared to a condition in which the prosthetic components may be implanted. Both proper surgical preparation of the bones and proper component selection are critical to the success of the procedure.
One condition which renders surgical preparation relatively difficult is the case in which the tibial canal of the patient""s tibia is offset from, or otherwise not coincident with, the center of the tibia. Indeed, it is known that the anatomy of some patients may create a situation in which the tibial canal of the patient""s tibia is offset from the center of the tibia by as much as three to four millimeters (3-4 mm). Such an offset is above and beyond a slight anterior-posterior offset of the tibial canal which is inherent in most patient""s anatomies. It should be appreciated that if a tibial implant having a stem which is centered relative to the implant""s plate is implanted into a patient""s tibia which has an offset tibial canal, undesirable impingement of the stem into contact with the cortical bone of the tibia may result.
As a result of these problems, a number of tibial components have heretofore been designed which include stems that are offset relative to the plate of the component. However, heretofore designed instruments for implanting such offset tibial components have often been difficult to use and often create a degree of uncertainty for the surgeon in regard to the positioning of the implant relative to the tibia.
What is needed therefore is a surgical instrument assembly which overcomes one or more of the above-mentioned drawbacks. What is particularly needed is a surgical instrument assembly which may be utilized to quickly, reproducibly, and accurately surgically prepare the tibia for implantation of a tibial component which has an offset stem.
In accordance with one embodiment of the present invention, there is provided a surgical assembly for preparing a tibia for implantation of a prosthetic implant. The surgical assembly includes a tray trial adapted to be secured to a proximal end of the tibia. The tray trial includes a plate having a plate opening defined therein. The plate opening has a center point. The surgical assembly also includes a first guide adapted to be secured to the tray trial. The first guide has a guide opening defined therein. The guide opening has a first bushing-receiving portion and a second bushing-receiving portion which is distinct from the first bushing-receiving portion. The surgical assembly also includes a drill bushing positionable in either the first bushing-receiving portion of the guide opening or the second bushing-receiving portion of the guide opening. The drill bushing has a bushing bore extending therethrough. The bushing bore has a center point. The center point of the bushing bore of the drill bushing is offset from the center point of the plate opening of the tray trial in a first direction when the drill bushing is positioned in the first bushing-receiving portion of the guide opening. The center point of the bushing bore of the drill bushing is offset from the center point of the plate opening of the tray trial in a second direction when the drill bushing is positioned in the second bushing-receiving portion of the guide opening.
In accordance with another embodiment of the present invention, there is provided a method of surgically preparing a tibia for implantation of a prosthetic implant. The method includes the step of securing a tray trial to a proximal end of the tibia. The tray trial includes a plate having a plate opening defined therein. The plate opening has a center point. The method also includes the step of securing a first guide to the tray trial. The first guide has a guide opening defined therein. The guide opening has a first bushing-receiving portion and a second bushing-receiving portion which is distinct from the first bushing-receiving portion. The method also includes the step of determining if a first drilled hole is to be offset in either a first direction or a second direction from the center point of the plate opening. The method also includes the step of positioning a drill bushing in either the first bushing-receiving portion of the guide opening or the second bushing-receiving portion of the guide opening based on the determining step. The drill bushing has a bushing bore extending therethrough. The bushing bore has a center point. The center point of the bushing bore of the drill bushing is offset from the center point of the plate opening of the tray trial when the drill bushing is positioned in either the first bushing-receiving portion of the guide opening or the second bushing-receiving portion of the guide opening.
It is therefore an object of the present invention to provide a new and useful surgical assembly for preparing a tibia for implantation of a prosthetic implant.
It is moreover an object of the present invention to provide an improved surgical assembly for preparing a tibia for implantation of a prosthetic implant.
It is a further object of the present invention to provide a new and useful method of surgically preparing a tibia for implantation of a prosthetic implant.
It is also an object of the present invention to provide an improved method of surgically preparing a tibia for implantation of a prosthetic implant.
It is yet another object of the present invention to provide a surgical instrument assembly which may be utilized to quickly, reproducibly, and accurately surgically prepare the tibia for implantation of a tibial component which has an offset stem.
The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings.